You might easily mistake it with the DS homebrew Earth Invaders, given that they are made by the same person, but, Earth Invaders 0: Before the Attack is homebrew made for the PSP and is smealum's entry to the Neoflash Summer Coding Contest

Download the latest version of MapThis! [Click Here]You can tell that Christmas is well and truly on the way with just about every famed PSP developer feeling the holiday spirit and releasing a new version of their applications;